Dispelling nutrition myths, ranting, and occasionally, raving

Tag Archives: fibre

PB&B sandwich photo by Kevin Reese. Used under a Creative Commons Licence.

After I wrote about the utter nonsense of food combining last week I had a reader contact me to suggest that perhaps I could elaborate on the positive side of food combining. To be clear, this is not what is traditionally meant by “food combining” which is a complicated way of eating which erroneously is believed to aid digestion and is more based on not eating certain foods in conjunction with others than with eating a variety of foods together.

I mentioned in my previous post that combining some foods can be beneficial in terms of absorption. Fat soluble vitamins (ADEK) need to be consumed with fat in order to be absorbed. This is one of the many reasons that a low-fat diet has been decried by dietitians. Skimmed milk with added vitamin D? No sense to it unless you’re washing down a croissant (or an avocado, nuts, or other fat-containing food of your choice).

In addition to aiding absorption of fat-soluble vitamins, certain foods can help with the absorption of other nutrients. Foods containing vitamin C can help with the absorption of iron, particularly from plant foods in which the iron is less bioavailable than in meats. For example, eating peppers with your spinach salad can help you to absorb more iron. Or having an orange with your oatmeal, tomatoes and beans, etc. Of course, there are also instances where nutrients can hinder the absorption of other nutrients. Tannins and fibre may decrease the absorption of some minerals and medications. Oxalate (found in spinach and some other fruits and vegetables) can impede the absorption of calcium.

As my astute reader pointed out, there’s also the benefit of glycemic control imparted by eating certain foods together. As any reader of Wheat Belly can (and likely will) point out to you, whole wheat bread has a higher glycemic index than white sugar. The thing that’s not taken into consideration when latching onto that fact is that we rarely eat whole wheat bread in isolation. Turn your bread into a peanut butter and banana sandwich or chicken salad sandwich and you’ve altered the glycemic load of the meal because you’ve added other macronutrients. Consuming fat, protein, or fibre can all help to mitigate the effect of carbohydrates on blood sugar. This is why, if someone with diabetes is experiencing low blood sugar it’s much better to give them candy or juice than a chocolate bar. On the flip-side, this is why most dietitians will recommend that you consume two food groups at snacks. Having a piece of fruit and a few nuts or cheese and crackers, berries and yoghurt, veggies and hummus… will help to prevent a spike in your blood sugar and keep you feeling full for longer that if you were to just have a piece of fruit. It also helps you to meet your nutrient needs if you include a vegetable or fruit as part of your snack.

A few weeks ago the media was reporting that apples may provide the cure for obesity. I was a little more sceptical. I mean, how many overweight and obese people do you know who eat apples? Probably lots. If apples were capable of curing obesity everyone would be thin.

My first concern was that this research was conducted on mice. That means that it may (likely) is not translatable to humans. A couple of things to consider: these mice were fattened up by being fed a very specific high-fat diet. Obesity is a complex condition with myriad factors. Unless the reason for people being overweight is due to consuming a similar diet to these lab mice, it’s quite likely that they will not respond to this weight loss treatment in the same manner as the mice. I also wondered how much apple the mice were fed. How much apple would humans need to consume to see similar results? Here’s where it gets crazy: themice did not eat the apples. Yep, that’s right. We have no idea how much apple would be beneficial to humans as we don’t know how much would be beneficial to mice. Rather than feeding the apples to the mice, the researchers made a slurry of apple compounds and mouse faeces. They found increased levels of certain bacteria that are commonly found in the faeces of slim mice in the cultured faeces of obese mice. Their results were not statistically significant. They showed a trend toward increased levels of some bacteria and butyric acid, and decreased levels of other bacteria in the faeces-apple slurries of obese mice but none of the changes (save the decreased bacteria) were large enough to be statistically significant.

It’s impossible to say whether or not eating apples (how many, how frequently) would have similar effects on the fecal microbiomes of mice or humans. We also don’t know if these microbial changes do occur if they would result in weight loss. Without knowing this, it’s a ridiculously huge leap to suggest that consuming apples could be a treatment for obesity. This didn’t stop the authors from concluding that:

These results suggest that dietary fibre and phenolic compounds remaining in apples after IVD might help to prevent metabolic disorders driven by an altered microbiota in obesity, and potentially protect from an obesity-disturbed balance of microbiota.

It also didn’t stop the media from publishing articles with headlines like: “An apple a day could keep obesity away: Granny Smiths promote friendly bacteria helping us feel fuller for longer” and “Granny Smith apples can help prevent the damage of obesity“.

I do think that research into our microbiomes is going to provide insight into many illnesses and conditions. However, our individuals microbiomes are extremely variable. Suggesting that this research using mice will translate to obesity treatments for humans. It’s also extremely unlikely that consuming one healthy food will negate the effects of an overall unhealthy diet. That being said, apples are nutritious and it’s certainly not going to hurt you to have an apple a day.

A few weeks ago, Dr Sharma shared this article (on twitter and on facebook), without comment. It’s an article by the dreaded Zoe Harcombe about why we shouldn’t be striving for at least five servings a day of fruit and vegetables. No, it’s not what you think. She’s not suggesting that people should have more than 5 servings of veg and fruit a day, she’s suggesting that people should have fewer servings of veg and fruit a day. “Great,” I thought, “Zoe strikes again“.

After working myself up into a bit of a rage about the article I noticed the date on it. January 2011. When I first saw that I thought that I wouldn’t blog about it after all as it’s not current. My second thought was, “whatever”. If I’m only seeing this for the first time there are probably others only seeing it for the first time as well.

Harcombe argues that recent research showing the lack of protection against myriad chronic diseases through increased vegetable and fruit consumption means that we should cease encouraging people to eat more vegetables and fruits. And everyone rejoiced and ate doughnuts for dinner and lived long and healthy lives dying peacefully from old age in their sleep! Dietitians, nutritionists, and other health professionals were suddenly out of work as there was no more chronic disease to contend with. If only.

In the article, Harcombe states, “no doubt some dieticians and nutritionists will reject my arguments. But science backs me up.”Well, she got the first part of that statement right, at least.

A great deal of Harcombe’s hypothesis centres around the assertion that vegetables and fruit don’t contain many vitamins or minerals. She concedes that vegetables do contain vitamin C and some A and K. Fruit apparently is only good for potassium. According to Harcombe, meat and other animal products are superior sources of most vitamins and minerals. This truly is a load of nonsense. Veg and fruit can be good sources of many vitamins and minerals. Not to mention the fact that they are usually good sources of water and can provide greater volume to your meal with few calories. Food is not just about individual nutrients. It’s about taste and texture and pleasure. Imagine eating a salad without vegetables. Think about the pleasure of eating a fresh blackberry off the brambles. How dull food would become if we didn’t have vegetables and fruit in our diets.

Harcombe moves on from her argument about the lack of vitamins and minerals in vegetables and fruit to say that some dietitians will argue that they are a source of antioxidants. She doesn’t object to this statement but instead says that she would rather not ingest oxidants in the first place. What was it that she said earlier? Oh yeah, “Science backs me up.” Might be time for a review of the oxidizing process, Zoe. If she’s avoiding oxidizing agents I want to know how she’s managed to survive without breathing air or drinking water. Our environment is chockfull of oxidizers. We should certainly avoid adding to them ourselves by avoiding smoking, excessive sun exposure, excessive alcohol consumption, etc. However, avoiding “chemicals” as Harcombe suggests is both ridiculous and impossible. Everything is chemicals. We are chemicals.

There is too much in this article to address it all. I mean, I could, but it’s too nice out as I’m typing this, and would you really keep reading if I went on and on? I just want to touch on one more issue with Harcombe’s vendetta against vegetables and fruit.

Harcombe takes issue with the belief that vegetables and fruit are important sources of fibre in our diets.

“The fact is, we can’t digest fibre. How can something we can’t even digest be so important to us, nutritionally?”

Apparently Harcombe doesn’t mind being constipated. Nor does she recognise the importance of fibre in prevention of heart disease. The desire to feel satisfied after a meal? Also not important. Even if these things are not important to her fibre serves other important organisms inside our bodies. That indigestible fibre is food for the bacteria living in our digestive tracts. Those same bacteria that provide us with things like vitamin B12, protect us against GI upset and harmful micro-organisms. We’ve only just begun to scratch the surface of the importance of our gut bacteria but it seems that they do a lot more for us than we ever realised.

So, if we are to listen to Harcombe and throw those five-a-day away, what are we to eat? Her top five foods: liver, sardines, eggs, sunflower seeds, and dark-green vegetables. That’s right. After telling us that vegetables and fruit are overrated and should be left for the rabbits, Harcombe then turns around and recommends vegetables in her top five foods. I rest my case.

A friend, and fellow dietitian, sent me the above screenshots. They were posted by a personal trainer. Of course it’s great to get people eating more vegetables and by no means do I want to discourage that. However, this is yet another example of why nutrition advice is best left to nutrition professionals.

Let’s start with the onions. High in fibre? It’s true, sort-of. Once cup of chopped onion contains a respectable 3 grams of fibre. Not exactly “high” but a “good source”. But… Who among us eats an entire cup of onion in a sitting? Certainly not I. At most, I would say I would have a couple of tablespoons. That brings the total fibre down to a whopping 0 grams. Oops. As for the other claims… Anyone telling you something is “great for fat loss” is probably full of it. No one food promotes fat loss. Following a healthy, adequate calorie diet, and healthy active lifestyle will promote fat loss (should you need to lose fat). Glutathione to reduce stress? Not according to WebMD. And just to be annoying, how on earth could eating onions reduce stress??? Will they ensure you don’t lose loved ones, keep your job, prevent moving? I think he must mean that they reduce the effect of stress on your body. Regardless, I’m pretty sure he’s mistaken. EWG did find pesticide residue on onions, however, they were ranked 50th (out of 51) so I’ll let him have that one; they are low in pesticides. Finally, onions do contain the prebiotic inulin. But, the onions aren’t what provide the benefits listed, the probiotics that use the prebiotics to grow are what provide the benefits. Both pre- and pro-biotics are needed to maintain a healthy digestive system.

I’ve blogged about the fallacy of weight loss resulting from the modern vegan diet before. As the gluten-free trend continues I frequently hear about people choosing to go gluten-free in order to lose weight. Many packaged gluten-free foods have a health halo. That is, people believe that they’re healthy simply because they’re gluten-free. However, the same rules apply to gluten-free packaged foods as to any other packaged foods and label-reading is still essential.

You may lose weight on a gluten-free diet. However, you’re much more likely to do so if you’re not replacing one processed packaged food for another. In fact, many packaged gluten-free foods often have more calories than their traditional glutenous counterparts. While gluten-free breads continue to evolve and improve in formulation, many are still very dense and while their slices may appear smaller than regular bread they may still have equivalent, or more, calories.

Beyond calories, gluten-free baked goods usually have less fibre than glutenous baked goods. Gluten-free bread tends to have about 1 gram of fibre per slice. Compare that to regular whole wheat bread which generally has about 4 grams of fibre per slice.

Before you decide to go gluten-free (without a doctor’s recommendation) remember that label-reading still applies. Ensure that you’re still getting sufficient fibre. Regardless of whether or not you’re going gluten-free, you should try to choose minimally processed foods as often as possible. Finally, gluten-free doesn’t mean calorie-free but it often means fibre-free.